A special resolution is one where to be passed no more than 25% of the people voting on the resolution, either by proxy or in person, vote against it. So the resolution is passed, provided no more than 25% of votes are against it.
This is distinct from an ordinary resolution that requires a vote of 50% or more to pass.
Some things require a special resolution, including waiving of interest on levy arrears, amending removing or adding by-laws, adding to or altering commono property (the notice board) and removing an EC member.